Various techniques and devices are known in the art for medical treatment of skin layers by application of electromagnetic energy, and in particular radio-frequency (RF) energy. The term “RF” is used broadly in the present patent application and in the claims to refer to electromagnetic waves at any frequency in the range between several kilohertz and several hundred gigahertz.
For example, PCT International Publication WO 2006/077567 ,whose disclosure is incorporated herein by reference, describes a system and method for heating biological tissue using RF energy. The system includes a RF source, phase shifter, impedance matching network and resonator connected to an applicator, which may be used in selective heating of cellulite bodies.
Some treatment techniques use a RF plasma discharge to deliver energy to the skin. For example, U.S. Patent Application Publication 2006/0189976, whose disclosure is incorporated herein by reference, describes a system in which a path of current from an electrode to the surface of the biological tissue to be treated is formed, thereby igniting a gas flow and forming a plasma gas-discharge. Electromagnetic interactions between the treated biological tissue and the plasma gas discharge traversing an electromagnetic interaction gap shape the profile of the plasma gas discharge. Other treatment systems using RF plasma generation are described in U.S. Pat. Nos. 6,105,581, 6,518,538, 6,629,974, and 6,723,091, whose disclosures are likewise incorporated herein by reference.
Some techniques and devices for treatment of skin layers use multi-electrode configurations to apply electrical energy to the skin at multiple points simultaneously. For example, U.S. Pat. No. 6,277,166, whose disclosure is incorporated herein by reference, describes a system and method for shrinking collagen in the dermis using a carrier with an array of electrodes. A microporous pad on the carrier, overlying the electrodes, contacts the patient's skin and ionically transports applied electromagnetic energy to ohmically heat dermal tissue beneath the epidermis. U.S. Patent Application Publication 2002/0120260, whose disclosure is incorporated herein by reference, likewise describes a tissue surface treatment apparatus in which a tissue contact surface has a plurality of apertures. Electrodes are advanced through the apertures and penetrate the skin in order to ablate tissue using RF energy.
As another example, U.S. Pat. No. 6,148,232, whose disclosure is incorporated herein by reference, describes a device for ablating the stratum corneum epidermidis of a subject. The device includes a plurality of electrodes, which are applied to the subject's skin at respective points. A power source applies electrical energy between two or more of the electrodes, in order to cause ablation of the stratum corneum for purposes of transdermal drug delivery or analyte extraction. Similarly, PCT International Publication WO 2005/096980, whose disclosure is incorporated herein by references, uses a device with a plurality of electrodes to create a pattern of perforations in one or more tissue layers.